HVACopediaBosch · Boiler · Domestic hot water
Combi comfort and economy modes
What happens, in order
- Comfort mode (default) heat exchanger is kept warm so DHW is instant, boiler may fire with no draw
- Economy mode (ECO lit) burner fires only when DHW is drawn
- On demand quickly open and close a tap to signal the boiler, then wait a short time for hot water
- In comfort mode, after preheating or a DHW call ends, the plate heat exchanger is reheated only after the cycle time
- After a DHW draw, space heating stays blocked for the constant DHW period
Timings and thresholds
| Item | Value |
|---|---|
| Cycle time keeping DHW hot (3.E) | 20-60 min, default 20 min |
| Constant DHW period (3.F) | 0-30 min, default 1 min |
Applies to: ZWB combi models
Models
More Bosch boiler sequences
- First power-up purge and trap filling · Startup
- Heating call, anti-cycle and pump post purge · Heating
- Tank priority (ZBR with DHW tank) · Domestic hot water
- Frost protection setup · Freeze protection
- Thermal disinfection of DHW tank · Other
Related
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Source: Bosch Greenstar 6721853955 (2025-11) and 6721853953 (2025-11), Heatronic service functions and operation sections. Written in our own words; timings can differ by model and software version, so check the manual for your exact unit.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.